Freshwater components track the export of dense shelf water from Prydz Bay, Antarctica

Abstract

Seawater samples were collected around Prydz Bay, Antarctica for measurement of stable oxygen isotopes (δ18O) in austral summer of 2013. Based on a three-end member mixing model of salinity and δ18O, the fraction of meteoric water (fMW) and sea-ice meltwater (fSIM) is estimated. Our results show that the average fMW varies from 0.5% to 3.0%, and decreases northward from the Amery Ice Shelf, while the average fSIM is small (−2.0%–1.0%) and shows the signal of brine-injected dense water, all of which indicate that the Prydz Bay shelf water is abundant with meteoric water and brine under the impact of ice-shelf water and intense sea ice formation. There is a continuous distribution of positive fMW and negative fSIM in the bottom water from the slope to the basin near Cape Darnley and Prydz Channel, which reflects the sinking of Dense Shelf Water (DSW) from Prydz Bay in the production of Antarctic Bottom Water (AABW). The contribution of DSW to AABW (fDSW) is estimated by mass balance of potential temperature, salinity and δ18O. The fDSW has a large spatial variation, with higher values near Prydz Channel (40–60%) and down-slope off Cape Darnley (70%), which confirms two routes for DSW export from Prydz Bay. Our study reveals the transport path of shelf water through freshwater components, and emphasizes the importance of shelf water of Prydz Bay in the formation of AABW.